Investigation On Repair Of Melt Damaged Tube-tubesheet Seal Weld Of Nuclear Steam Generator

Now, seal welding of nuclear steam generator is performed by automatic welding machine. In the manufacturing process it is likely to cause tube hole sealing weld quality problem due to the welding equipment or other causes. Applied research of tube hole sealing weld damage repair could resolve current problems encountered. To promote the technology development of China's nuclear power equipment manufacturing is significant, and may also enrich the seal weld repair methodology.American Society of Mechanical Engineers Part IX related procedures the program can be used when forging material and weld heat treatment is not applicable a variety of pressure vessels. Specification provides welding procedures and quantity control standards. Defects must be removed by grinding or mechanical methods, but nut by thermal cutting. Welding must be according to semi-bead repair welding procedures.In this paper, some repair technology research for sealing tube holes melt damage for steam generator of one nuclear power equipment manufacturing company was undertaken for CPR1000 nuclear steam generator. This paper presents a series of experiments and studies using tempered weld repair methods which have practical engineering significance of repair techniques.First, the author analyzed the state of the art of the steam generator melting damage and melting damage causes and seal weld bead tempering repair principle. And found that a temper bead welding cycle generates heat affected zone is formed on the cladding layer tempering effect. Else, the material requirements, welding parameters were tested and the test results for chemical analysis, macroscopic examination, microscopic examination, hardness testing and residual stress testing obtained. The results show that the tempering bead repair may lead to base metal of heat affected zone melting damaged hole with better impact toughness, hardness and residual stress to meet the requirements. Tempering bead welding technique as an effective method of partial replacement of weld heat treatment may significantly improve the micro structure and performance of coarse grain HAZ region, it has a good prospect of engineering application. The results showed that the research work carried out by the author is successful feasible.Results for product surface residual stress measurement method with stress test showed that the welding area stress is compressive which may improve the welding area anti-fatigue properties in the region, and also reduce the stress corrosion sensitivity of the region.